In a lithography process, a lithography mask (reticle) having a predetermined pattern is first fabricated, the mask is then used to transfer the pattern on a photoresist layer disposed on a wafer (substrate). The mask making process is an important part of the processes of manufacturing semiconductor devices. The mask fabrication is one of the highest costs of the semiconductor manufacturing processes and also one of the bottlenecks that limits the minimum feature size of the semiconductor devices.
Currently, the manufacturing process of a lithography mask includes forming a chromium film on a transparent (light transmissive) glass, an electron beam (e-beam) lithography resist layer is formed on the chromium film, then a pattern is directly written to the resist layer by an e-beam, which is controlled by mask layout software to form a mask pattern on the resist. Finally, the mask is etch to form a patterned mask. However, in the actual manufacturing process, due to environmental pollution and other reasons, the mask is not perfectly etched, resulting in an imperfect patterned mask having some defects.
Conventional methods for repairing masks, such as binary masks, or phase shifting masks (PSM) mainly utilize a focused electron-beam induced etching with xenon difluoride (XeF2), or gallium (Ga) focused ion beam with FeI2 and I2 to directly repair the mask defects. However, as shown in FIG. 1, for masks using advanced materials, such as molybdenum silicide (MoSi) binary masks (e.g., opaque MoSi on Glass (OMOG) masks), the repair techniques of using a focused electron beam with XeF2 or Ga focused ion beam with FeI2 and I2 may introduce some uncertainty, so that a desired (good) portion of the mask may be etched away, or a bad (undesired) portion cannot be removed by etching. FIG. 1 has a top portion showing cross-sectional views of an OMOG mask before and after repair and a bottom portion showing four example pictorial diagrams of the mask subject to repair uncertainty: example diagram denoted “1” shows a circle instead of a cross, example diagram denoted “2” shown more nearly circular than square, example diagram denoted “3” shows a nearly open, and example diagram denoted “4” shown nearly a bridge between two adjacent lines. Thus, convention repair methods cannot effectively repair mask defects.
Thus, there is a need to provide a novel mask repair method and a mask to overcome the above-described drawbacks.